The present invention relates to an armrest assembly for a chair and, more particularly, to an armrest assembly for a chair allowing adjustment of a position of an armrest unit in the length, width, and height directions.
A conventional chair armrest assembly generally includes a support rod fixed to the chair body and an armrest mounted on top of the support rod for supporting an arm of a user. Adjusting devices for adjusting the position or height of the armrest have been proposed, and U.S. Pat. No. 7,387,341 discloses an example of the adjusting devices. Specifically, an armrest assembly of a chair disclosed in U.S. Pat. No. 7,387,341 includes a fixing board, a first movable board, two limit plates, a second movable board, a positioning body, a restoring spring, a lining, a foam body, a push button, a bottom cap, and two shading plates. The fixing board includes a plurality of positioning holes. The push button can be pressed to disengage the positioning body from the positioning holes to allow adjustment of the position of the foam body in the length direction and the width direction. After adjustment, the push button is released to engage the positioning body into one of the positioning holes. However, the armrest assembly is complicated in structure. Furthermore, the adjustment is restricted by the locations of the positioning holes.
In another approach, the support rod includes a plurality of engagement holes spaced from each other in the vertical direction. When the armrest moves upward or downward, an engagement member moving together with the armrest engages with one of the engagement holes to position the armrest. However, the spacing between the engagement holes does not allow exact position adjustment of the armrest in the vertical direction.
U.S. Pat. No. 7,661,763 discloses an armrest including a support arm mounted on a sleeve movably mounted on a support post. A locking member is fixed to an upper end of the support rod and includes a semi-circular locking hole. A control knob and a movable shaft are mounted to the sleeve. The movable shaft includes an arcuate portion with vertically spaced locking teeth selectively engaged with a rectilinear locking side of the locking hole. The control knob can be pressed to rotate the movable shaft through an angle to a position in which the arcuate portion is aligned with an arcuate side of the locking hole, allowing the movable shaft to move in the vertical direction for adjusting the height of the support arm. However, the spacing between two adjacent teeth of the movable shaft does not allow exact height adjustment. Furthermore, adjustment is not easy if the arcuate portion of the movable shaft is not exactly aligned with the arcuate side of the locking hole.